Bill Gates recently called Steven Pinker's new book, "Enlightenment Now," his "favorite book of all time." Pinker — a professor of psychology at Harvard and the author of a number of popular science titles — takes a sweeping look at human history and comes to the optimistic conclusion that we're living in the most peaceful era humans have ever enjoyed.

He analyzes 15 indicators, like literacy, quality of life, and safety, and compares data to show how they have changed over time. Despite the doom and gloom we often see in the news, Pinker's findings are astounding. By all the measures he looks at, humans are much safer than ever before.

On his blog, Gates highlights what he thinks are the five most interesting facts from Pinker's book, and how they illustrate the ways the world is improving for the better.

1/

Time spent doing laundry fell from 11.5 hours a week in 1920 to 1.5 hours in 2014.

Tim Boyle/Getty Images

Technological innovations in the home have freed up people — especially women — to pursue "higher callings," like entering the workforce, pursuing advanced degrees, and creating art, Pinker writes.

The average time Americans spent washing their clothes has fallen from 11.5 hours a week in 1920 to only about 1.5 in 2014, according to Pinker. He quotes Hans Rosling, a renowned physician and public-health scholar, who says that the washing machine is the "greatest invention of the Industrial Revolution" for effectively giving people one day a week of their lives back.

But it's not just laundry where we're saving time. The average time Americans spent on housework has fallen fourfold since 1900, from 58 hours a week — more time than a full-time job — to 15.5 hours in 2011, according to Pinker.

"But in most times and places housework is gendered, so the liberation of humankind from household labor is in practice the liberation of women from household labor," Pinker writes.

We have modern appliances, like refrigerators, microwaves, vacuum cleaners, and, yes, washing machines, to thank for that.

2/

You’re much less likely to die on the job than in the past.

Thomson Reuters

Thanks to a push from engineers, lawmakers, unions, and journalists exposing how fraught the manufacturing-based workplaces of the early 20th century were, Americans are far less likely to die on the job than ever before.

In 1910, almost 70 American workers per 100,000 died on the job. That number has fallen to fewer than 5, according to Pinker's research. This figure belies the recent nostalgia in political circles for a return to the US's manufacturing-based economy.

"With the shift from a manufacturing to a service economy, many social critics have expressed nostalgia for the era of factories, mines, and mills, probably because they never worked in one," Pinker writes. According to Pinker, early reforms like employers' liability and workers' compensation were instrumental in incentivizing the creation of safer workplaces.

3/

You’re 37 times less likely to be killed by a bolt of lightning than someone at the turn of the century.

Reuters/Steve Marcus

"Humanity's conquest of everyday danger is a peculiarly underappreciated form of progress," Pinker writes, and that's most evident in how much less likely we are to die from lightning strikes.

Because of advances in weather prediction, education, medical treatment, and safety systems (including lighting-strike mitigation on houses and buildings), Americans are 37 times less likely to be killed by a lightning strike than they were just over 100 years ago.

Lightning strikes are just one example of how much less likely humans are to die from any sort of natural disaster. The annual death rate for natural disasters in higher-income countries in the 1970s was 0.09 per 100,000 people, and that's almost been cut in half, to 0.05, owing to greater safety standards, disaster response, and predictive tools. For poorer countries, that number is much higher, at 0.02 per 100,000, though it's been cut from 0.7 in the past five decades, according to Pinker's research.

4/

The global average IQ score is rising by about 3 IQ points every decade.

Natalie Behring/Getty Images

Global IQ scores have increased by an average of three points a decade, the clearest sign we have yet that people are actually getting smarter, Pinker writes.

While intelligence is a highly heritable trait, improvements in nutrition, medicine, and cleaner environments have given our brains much more energy to develop over time. But that's not the only explanation for the rising trend. Pinker writes that of all the subtypes of intelligence that the IQ tests for, it is the "abstract, fluid kinds of intelligence" that have shown the largest increases in the past decade.

These are defined as analytic thinking, like understanding and reasoning, and relating abstract objects to larger categories, and the increase is owed in part to widespread, high-quality education.

"A high IQ is not just a number that you can brag about in a bar or that gets you into Mensa; it is a tailwind in life," Pinker writes, adding that people who score higher on intelligence tests end up getting into better schools, scoring better jobs, and earning more money over time.

5/

War is illegal.

REUTERS/Joe Penney

War between nation states — and the genocides and atrocities that came with it — is largely a thing of the past.

In the late 1940s, after the end of World War II, almost 25 people a year died violent deaths in battle. That number has fallen to fewer than 5, with a recent uptick a result of the Syrian Civil War, according to Pinker.

And in terms of genocide, it appears we as a society really did learn a lesson from the Holocaust. The rate of death due to genocide has cratered since the 1940s, from well over 350 per 100,000 at its peak, to well under 5 today, according to Pinker.

The reason for this is that war, as conventionally defined, is largely illegal. Before the era of international bodies like the UN and complex, multiparty-trade agreements, the adage about warfare rang true:

"Might made right, war was the continuation of policy by other means, and to the victor went the spoils," writes Pinker.

Today, the world's nations have committed to not pursuing warfare for territorial gains or policy objectives, unless it is in self-defense or with the blessing of the UN's Security Council. While war still exists within states, and against nonstate actors like terrorist groups — and the norm is sometimes breached — traditional warfare between states is largely a thing of the past.